U.S. Pat. No. 3,004,863 to Gray et al teaches increasing the scratch resistance of glass by applying to the glass surface an acidic aqueous solution of an organic titanate ester composition and heating at a temperature sufficient to anneal the glass.
U.S. Pat. No. 3,582,395 to Adams et al discloses a method for increasing the scratch resistance of glass by treating the surface at a temperature between the strain point and the softening point with an alkylsilyl titanate to form a protective coating of silica-titania.
U.S. Pat. No. 4,242,403 to Mattimoe et al describes multilayer automotive glazing units that include transparent substrates with protective covers, and that combine penetration resistant body portions with abrasion resistant surfaces of a silica-reinforced organopolysiloxane.
U.S. Pat. No. 4,275,118 to Baney et al discloses a coating composition comprising an acidic dispersion of colloidal titania, colloidal silica and hydroxylated silsesquioxane in an alcohol-water medium which produces a hard, abrasion-resistant coating when cured on a plastic substrate such as polycarbonate.
European patent application No. 85110293.9 published 05.02.86 discloses carbon-containing monolithic glasses prepared by a sol-gel process involving a partial condensate of a silanol containing colloidal metal oxides such as SnO.sub.2 B.sub.2 O.sub.3 and ZnO.sub.2.
U.S. Pat. No. 4,405,679 to Fujioka et al discloses a coated shaped article of a polycarbonate type resin of improved abrasion resistance comprising a shaped polycarbonate substrate, an undercoat applied and cured on the substrate, and an overcoat applied and cured on the undercoat comprising a hydrolyzate of an epoxy-containing silicon compound, at least one member of the group of hydrolyzates of organic silicon compounds, colloidal silica and organic titania compounds, and a curing catalyst.
U.S. Pat. Nos. 4,500,669 and 4,571,365 to Ashlock et al disclose transparent, abrasion-resistant coating compositions comprising a colloidal dispersion of a water-insoluble dispersant in a water-alcohol solution of the partial condensate of silanol wherein the dispersant comprises metals, alloys, salts, oxides and hydroxides thereof.
U.S. Ser. No. 915,344 to Lin et al, and U.S. Ser. No. 914,856 to Yoldas et al filed on even date herewith disclose silane/alumina, silane/titania and silane/zirconia sol-gel coating compositions. These coatings improve the abrasion resistance of surfaces of organic polymers such as acrylic and polycarbonate.